The present invention relates to an arrangement for the synthetic testing of high voltage switches, the arrangement being of the type including a high current, low voltage direct voltage source, an auxiliary switch, an inductance and the switch to be tested, and an auxiliary voltage source having a low current and high voltage output which stresses the switch to be tested to its voltage breakdown level.
When a high voltage direct current in a high voltage direct current transmission network is interrupted by the opening of a switch, the switch must absorb the energy stored in the lines and in the smoothing chokes of the network and must work against the driving voltage of the network.
To simulate the stresses occurring in the test field under such conditions various synthetic test circuits are known.
Thus, the direct current required for testing can be obtained from an a.c. generator which operates at a reduced frequency, as disclosed in German Pat. No. 1,046,185. The current whose peak value is approximately constant is then considered to be a direct current. The recurring voltage at the switch to be tested is generated by an additional direct voltage source which is applied across the switch to be tested at the moment when the first-mentioned current becomes zero. A discharge of the direct voltage source into the high current circuit is prevented by an auxiliary switch in the high current circuit.
It is also known to simulate the switch stresses occurring during the switching-off process in test circuits with inductive storage, as disclosed in the German periodical (ETZ-A, Volume 93 (1972), Issue No. 3, page 164, FIG. 7a). In this circuit an inductance is charged by a direct voltage source of low voltage and the energy stored by the inductance is then converted in the switch to be tested. The high voltage occurring during the switching-off at the switch to be tested is produced predominantly by the inductance. The deviation in the stress placed on the switch to be tested with respect to the current waveform and the energy absorption during the switching-off process as a result of the reduced driving voltage when compared to real conditions can be compensated in part by a value of the inductance, which is greater than that present under real conditions.
The recurring voltage in the known process is simulated by an additional high-resistance auxiliary voltage source which is permanently connected to the switch and stresses the switch, after the switching-off process, to its voltage resistance, or breakdown value. An auxiliary switch can be used to isolate the high current circuit after the current has reached zero.
Due to the absence of the driving voltage, the simulation of the current waveform when it becomes zero and the waveform of the transient voltage at the switch only incompletely correspond in this method to the real conditions.